The present invention relates to a method and apparatus for mounting a femoral stem hip prosthesis in a femoral canal with the use of a cement. In U.S. Pat. No. 4,357,716, issued Nov. 9, 1982, it is pointed out that there are a great many problems involved in mounting the femoral stem hip prosthesis in the femoral canal with the use of cement and there is disclosed therein a device which holds the prosthesis in a fixed position relative to the femur while cement is applied to the femoral canal under pressure and allowed to set.
This device requires the use of a base guide which is rigidly attached to the femur and which not only enables the surgeon to determine the proper angle at which to resect the head and neck of the femur but also provides the base for attachment of other components which enable cement to be applied to the femoral canal under pressure. The base guide is attached to the femur in the location of the lesser trochanter with pins extending through portions of the cortex of the femur. These pins may be Kirschner wires or any other fixation device such as Steinmann pins or small drill bits and the like. The base guide is generally U-shaped and has orifices in each side thereof that are opposed and axially aligned. The pins pass through the orifice in one side, the femoral cortex and the opposing orifice in the other side of the guide.
The orifices are made only slightly larger than the Steinmann pins and while this method and apparatus performs the function for which it was intended, it has been found that if there is any slight misalignment of the pin as it passes through the femoral cortex, it may not precisely line up with the orifice on the opposite side of the U-shaped guide. Thus, the pin may strike the guide itself instead of the orifice thereby requiring the pin to be reset. Not only, then, is a problem created in getting the pin to pass directly in alignment from one orifice to the other but also increased time for the surgery is required.
The present invention overcomes this disadvantage by providing a first orifice in the guide for inserting a pin and a second opposing orifice in the guide much larger in cross section than the pin and inserting in the second receiving orifice an easily penetrable material such as a cylindrical plastic plug whereby the pin in passing through the first inserting orifice and the femoral cortex, may deviate from axial alignment and still strike the plastic plug in the receiving orifice and pass therethrough. Thus, the metal frame of the base guide is not touched and yet the pin may deviate somewhat from the axial alignment and still penetrate the plastic plug. The plastic plug is threaded and so is the second receiving orifice in which it is inserted so that after the base guide has been used in one operation, the plastic plug can be threadably removed and a new one threadably inserted so that the guide can be used again in the next operation.
In addition, instead of using Kirschner pins or Steinmann pins, an elongated drill bit having approximately the same outside diameter as the Kirschner or Steinmann pins are used. Thus, by using the small drill not only does the drill bit pass easily through the femoral cortex with a minor amount of deviation but it also easily penetrates the plastic plug in the second receiving orifice thus enabling the base guide to be securely attached to the femur in a rigid relationship. Obviously, other opposed pairs of axially aligned orifices could be placed in said U-shaped guide as disclosed in U.S. Pat. No. 4,357,716 wherein the receiving of the orifices is larger than the attaching pin and has a cylindrical plastic plug removably threaded therein to allow a drill bit, serving as an attaching pin, to pass from the first pin insertion orifice to the second pin receiving orifice with deviation from the axial alignment without striking the metal guide.
Thus, it is an object of the present invention to provide an improved U-shaped base guide for rigid attachment with at least one pin through the femoral cortex to the proximal end of a femur as a guide for removing the neck of said femur.
It is also an object of the present invention to provide at least a first pin insertion orifice in one side of the U-shaped guide, a second pin receiving orifice in the opposite side of the U-shaped guide in axial alignment with the first orifice and a plastic plug threadedly inserted in the second orifice and being easily penetrable by the pin so that the pin may deviate from axial alignment between the first and second orifices without striking the base guide.
It is also an object of the present invention to use a drill bit in place of a Kirschner pin or a Steinmann pin so that penetration of the femoral cortex and of the plastic plug insert in the second orifice is more easily accomplished.